AK: I did look for specs of plane on GSP website, but it seems to be discontinued. You mentioned that some planes are designed to have servos mounted to balsa structures. I am not familiar with any, can you give a couple of examples. Most builders that I know or have come into contact with use some type of hard wood, but again my experience is limited and I am seeking to learn.

No questions, 90-120 size plane especially on control surfaces should use plywood.
In 2 of my Prop Jets designs servos attached to balsa blocks. It never failed for me...

ak-models.com/su27.htm
ak-models.com/mig29.htm